Understanding Async Programming with Starbucks

Helpful post to get a better understanding of Asynchronous programming.

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've worked and trained with many developers over the years, and I found that many people struggle to get their head around asynchronous programming. Asynchronous structures like Futures, Promises and Blocks are literally everywhere now. Yet, they're still difficult to understand, so I thought I can help you wrap your head around it with some help from Starbucks. That said, grab your Pumpkin Spice Latte and get ready for a Caffeine-fueled adventure through the world of Async programming ☺

Pre-Starbucks - The Synchronous Model

Let's take a moment to picture yourself in line at your favorite coffee store, where they can process only one transaction at the time. You get to the counter, what happens next?

  • You put in an order for a quadruple espresso (it's going to be a long day ahead)
  • You pay the extortionate price (when did coffee get so expensive?!)
  • You stand still...
  • While you stand your server goes and crushes some beans;
  • You stand still...
  • The barista turns some handle's, bangs a big metal thing loudly, steams, froth;
  • You stand still...
  • Everyone behind you stands still...
  • The barista holds the little paper cup under the coffee machine as it pours your drink in;
  • Everyone behind you waits, checking their phones/watches, wondering who the awkward person ordering a quadruple espresso is;
  • Finally, the barista gives you your coffee;
  • You grab your drink; add any additions of your choice and leave;
  • Now the Server moves on to the next person, who orders a single bottle of water they've been holding the entire time, they pay and leave immediately!

Welcome to the world of synchronous programming! You ask a function to do something and you wait until they've done it. And if someone else wants to do something that could be much quicker, they have to wait!

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